A description of the final stadium larva ofLeptogomphus elegansLieftinck, with a discussion of taxonomic characters of the larvae of the genusLeptogomphusSelys (Odonata: Gomphidae)

2012·0.14 MB·

by  Qi-Han Xu

InternationalJournalofOdonatology
Vol.15,No.1,March2012,25–29
A description of the final stadium larva of Leptogomphus
elegans Lieftinck, with a discussion of taxonomic characters
of the larvae of the genus Leptogomphus Selys
(Odonata: Gomphidae)
Qi-HanXu*
DepartmentofBiologicalandEnvironmentalEngineering,ZhangzhouCityUniversity,Zhangzhou,
Fujian363000,PRChina
(Received10December2011;finalversionreceived7January2012)
ThefinalstadiumlarvaofLeptogomphuselegansLieftinckisdescribedandillustratedforthefirsttime.
ThetaxonomiccharactersofthelarvaeofthegenusLeptogomphusSelysarediscussedandsummarized.
Keywords: Odonata;dragonfly;LeptogomphuselegansLieftinck;LeptogomphusSelys;larva;taxonomic
characters
Introduction
The genus Leptogomphus Selys, 1878, includes 23 known species (Schorr & Paulson, 2011),
occurringinChina,Japan(RyukyuIslands),India,Bangladesh,SriLanka,Myanmar,Thailand,
Indochina and Sundaland (Chao, 1990, p. 284). Among them, L. elegans Lieftinck, 1948, is
endemictosouthernChina,distributedinFujian,GuangdongandGuangxi(Wilson&Xu,2009).
Todate,onlythelarvaeofL.hongkongensisAsahina,1988,L.lansbergeiSelys,1878(including
both L. l. lansbergei Selys, 1878, and L. l. assimilis Krueger, 1899), L. sauteri Ris, 1912, and
L.yayeyamensisOguma,1926,havebeendescribed(Ishida,1996,pp.257–258;Lieftinck,1948;
Matsuki,1978,1996).ThechiefcharactersoftheLeptogomphuslarvaehavebeensummarizedby
Lieftinck(1948),Chao(1990,p.285),andIshida(1996,p.257)respectively,buttheirobservations
differfromeachotherinseveralrespects.Inthepresentpaper,thefinalstadiumlarvaofL.elegans
is described and illustrated for the first time, and, based on a comparison of morphological
characters among five known Leptogomphus larvae, the taxonomic characters of the larvae of
genusarediscussedandreviewed.
*Email:[email protected]
ISSN1388-7890print/ISSN2159-6719online
©2012WorldwideDragonflyAssociation
http://dx.doi.org/10.1080/13887890.2012.663677
http://www.tandfonline.com
26 Q.-H.Xu
Descriptionofthefinalstadiumlarvaof LeptogomphuselegansLieftinck,1948
Specimensstudied
In total nine larvae: 5(cid:2), 4(cid:3), Fujian Province, Zhangzhou City, Mountain Tianbao 24◦ 39(cid:3) N,
117◦ 31(cid:3) E,3May2007,leg.Xu,depositedintheDepartmentofBiologicalandEnvironmental
Engineering, Zhangzhou City University, Fujian, China.Their identity was confirmed by com-
parisonwiththeexuviaefromwhichanadultmalehadjustemerged,whichwasobservedand
collectedinthefieldatthesamelocality.
Descriptionofthefinalstadiumlarva(Figure1)
Amedium-sizedgomphidlarvawithaflattenedovoidbodyasshowninFigure1a.
Head. Roughly pentagonal in shape, widest across eyes, which are comparatively large and
slightlylaterallyprotuberant.Fronsinfrontwithasquarishprojection.Occipitalmarginarched
inwards.Antenna (Figure 1b) 4-segmented, slightly longer than the distance between the two
antennae; segment 1 (scape) thickened with rounded margins; segment 2 (pedicel) short and
narrow;segment3flattenedandnarrowlyovoid,slightlycurvedupwards,andnearlytwicethe
lengthofsegments1+2;segment4vestigial,button-like.Labiumshort,extendingposteriorlyto
thelevelofthebasalprocoxae.Prementum(Figure1c,d)slightlylongerthanwide,medianlobe
very slightly curved on anterior border, edged with a row of about 20 brownish black squarish
serrations, each bearing a cluster of long brown hairs; labial palps short and robust, broad at
base, gradually narrowed toward blunt apex, the inner margin incurved slightly, with 11–12
strong serrations; movable hook incurved, about twice the length of terminal hook of palp, its
apexsharp.
Thorax. Prothorax narrower than head, with a pair of small lateral spines on dorsum. Legs
short,robust,bearingdensebrownhairs.Profemurandmesofemurincurvedslightly,metafemur
straight,reachingbaseofabdominalS4;protibiaandmesotibiawithfossorialspinessubapically;
clawsstrong,evenlycurved.Wingsheathsstronglydivergent,tipsofhindwingsreachingbase
ofabdominalS4.
Abdomen. Oblong,roof-shapedincross-section,widestacrossS6.Apicalsegmentsevenlynar-
rowed. S1 very short; S2–8 equal in length; S9 distinctly longer than S8 and about three times
as long as S10. Dorsal tubercles present on S2–9 (Figure 1e), all directed backwards.Tubercle
onS2highest,stick-shaped;remainingtubercleslessprominentandbecomingshortergradually
from S2 to S8, and S9 with only a trace of dorsal protuberance on its distal margin. Lateral
spinespresentonS7–9;thoseonS7–8small,andthoseonS9large,triangular.Analappendages
(Figure 1f) small and short, about twice the length of S10. Epiproct slightly longer than wide,
with pair of tubercles at two-thirds the distance to apex; cercus acuminate, a little shorter than
epiproct;paraproctlongerthanepiproct,broadatbaseandbluntatapex.Colourpatternofdorsum
ofabdomenasshowninFigure1a.
Measurements[mm]. Totallength25.2–27.5,greatestwidthofhead5.1–5.6,lengthofantenna
2.4–2.6, length of metafemur 4.5–5.1, length of hind wing sheath 6.7–7.1, length of abdomen
15.8–16.5,greatestwidthofabdomen7.9–8.1;n=9.
AdescriptionofthefinalstadiumlarvaofLeptogomphuselegans 27
Figure 1. ThefinalstadiumlarvaofLeptogomphuselegans:(a)habitus,dorsalview;(b)antenna,dorsalview;(c)
prementum,ventralview;(d)laterallobeandanteriorborderofprementum,ventralview;(e)abdominaldorsaltubercles,
lateralview;(f)analappendages,dorsalview.
Differentialdiagnosis
Of the five known Leptogomphus larvae, that of Leptogomphus elegans is closer to that of
L. hongkongensis than to those of the other three species. The first two share many morpho-
logical characters, e.g., larger body size; third antennal segment longer than wide, in the ratio
of 2:1; prementum slightly longer than wide; median lobe of prementum with row of about 20
squarishserrations;dorsaltuberclespresentonS2–9,andthatonS9discerniblypresent.
ThelarvaofL.eleganscanbeseparatedfromthatofL.lansbergeibyhavingdorsaltubercles
present on S2–9; from those of L. lansbergei and L. yayeyamensis by having dorsal tubercles
invariablypresentonS9;andfromthoseofL.hongkongensisandtheotherthreespeciesbythe
followingtwomajorcharacters:(1)dorsaltuberclesonabdominalS2–8allobviouslyprotruding
upwardsandbackwards,andthoseonS2–4allfinger-shaped,bluntattip;(2)abdominaldorsum
28 Q.-H.Xu
withdistinctivecolourpattern,namely,S3–8allwithapairofbrownbasaldotsondorsum,S9
withalargeblackishbrownreticularcentralmarkingondorsum.
Biologicalnotes
AlllarvaeofLeptogomphuselegans werecollectedfromasmallstreamwhichranthroughthe
woodsatanelevationofc.400masl.Theywerefoundburieddeepinthesand.InFujianadults
firstappearinAprilandtheflyingseasonendsinAugust.
DiscussionoftaxonomiccharactersofthelarvaeofgenusLeptogomphusSelys
Lieftinck(1948),Chao(1990,p.285),andIshida(1996,p.257)allsummarizedthechiefcharac-
tersofLeptogomphuslarvae,buttheirremarksdifferfromeachotherinseveralrespects.Based
onstudyofthelarvaeofL.lansbergeilansbergeiandL.l.assimilis,Lieftinck(1948)describedin
detailthechiefcharactersofthelarvaofMalaysianLeptogomphus.Hismainpointsmaybelisted
as follows: (1) body flat, leaf-like; (2) antennae four-jointed, the third joint flattened, narrowly
oval, the fourth joint vestigial; (3) labium short and squarish; median lobe almost straight on
anteriorborder,bearingadenserowofbristles;labialpalpsmallbutstout,innermarginstrongly
serrate; (4) wing-sheaths strongly divergent, reaching back as far as the end of segment 4; (5)
dorsaltuberclespresentonS1–7(l.lansbergei)or1–8(l.assimilis);lateralspinesonS7–9;Chao
(1990,p.285)listedthechiefcharactersoftheLeptogomphuslarvaeasfollows:(1)thethirdanten-
nal segment flat and wide, the length about twice the width; (2) anterior border of prementum
comparativelystraight,bearingarowofabout20squarishserrations;(3)wing-sheathsdivergent
backwards;(4)abdominalsegments2–9withdorsaltubercles,abdominalsegments7–9withlat-
eralspines.Obviously,Chao’snotesabovewerechieflybasedonthemorphologicalcharactersof
thelarvaofL.sauteri.Ishida’s(1996,p.257)summaryofthecharactersofLeptogomphuslarvae
largelyfollowedLieftinck(1948).HenotedthatLieftinckdidnotmentionarowofserrationson
theanteriorborderoftheprementum,whichisobviouslyserratedinthelarvaeofbothL.sauteri
andL.yayeyamensis.
ThelarvaeofL.elegans,L.hongkongensis,L.sauteriandL.yayeyamensis,whichwerefound
after that of L. lansbergei, do not agree closely with Lieftinck’s (1948) characterization of the
larva of Malaysian Leptogomphus. For example, the wing-sheaths of L. elegans, L. hongkon-
gensis, L. sauteri and L. yayeyamensis are all shorter than those of Malaysian Leptogomphus,
whichreachbackasfarastheendofabdominalS4;thelarvaeofL.elegans,L.hongkongensis,
L. sauteri and L. yayeyamensis all have dorsal tubercles present on abdominal S2–9, whereas
MalaysianLeptogomphushavedorsaltuberclespresentonabdominalS1–7(L.l.lansbergei)or
1–8(L.l.assimilis);inthelarvaeofL.elegans,L.hongkongensisandL.sauteritheprementum
isslightlylongerthanwide,butinMalaysianLeptogomphusthisstructureisshortandsquarish.
Moreover,Chao’s(1990,p.285)listofthechiefcharactersofLeptogomphuslarvaedoesnot
match the larvae of L. elegans, L. hongkongensis, L. lansberge and L. yayeyamensis in several
respects.Forexample,thethirdantennalsegmentinthelarvaofL.yayeyamensisislongerthan
wide,inaratioof1.5:1(Ishida,1996,p.80,figure675),butnot2:1asnotedinChao’ssummary;
theanteriorborderofprementuminthelarvaofL.yayeyamensisbearsarowofabout17serrations
(Ishida,1996,p.71,figure534),not20asnotedinChao’ssummary;thelarvaofL.lansbergei
hasdorsaltuberclespresentonabdominalS1–7(L.l.lansbergei)or1–8(L.l.assimilis),not2–9
asnotedinChao’ssummary.
BasedonthecomparisonanddiscussionofmorphologicalcharactersamongfiveknownLepto-
gomphuslarvaeabove,themajortaxonomiccharactersofthelarvaeofgenusLeptogomphusSelys
AdescriptionofthefinalstadiumlarvaofLeptogomphuselegans 29
canbetentativelyredefinedasfollows:(1)bodyflat,narrowlyoblong;(2)antenna4-segmented,
thethirdsegmentflattened,narrowlyoval,thefourthsegmentvestigial;(3)anteriorborderofpre-
mentumcomparativelystraight,bearingarowofsquarishserrations;(4)wing-sheathsstrongly
divergent backwards; (5) dorsal tubercles present on most abdominal segments, lateral spines
presentonS7–9.
Acknowledgements
IamgratefultoProfZai-FuXu,DrLiang-JongWang,DrAlbertOrrandMrAkihikoSasamotofortheirkindhelpin
providingliteraturenecessaryforthepresentstudy.IalsothankDrAlbertOrr,MrAkihikoSasamotoandananonymous
reviewerforrevisingandimprovingthemanuscript.
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